1. Field of the Invention
The invention relates to a vehicle control system that is configured to control behavior characteristics or acceleration/deceleration characteristics (which will be called “running characteristics”) of the vehicle, such as a power characteristic, steering characteristic and a suspension characteristic of the vehicle, so that the running characteristics match a running environment and driver's preferences and intention regarding running.
2. Description of the Related Art
While the vehicle behavior, such as a vehicle speed and a running direction, varies according to the driver's accelerating/decelerating operation and steering operation, the relationship between the amount of the driver's operation and the amount of change of the behavior is determined not only by the energy efficiency, such as a fuel efficiency, but also by characteristics, such as a ride comfort, quietness and power performance, which are required of the vehicle.
In the meantime, environments in which the vehicle runs include a wide variety of surroundings or road types, such as an urban area, an expressway, a winding road, an uphill, and a downhill, and there are a variety of driver's preferences and intentions regarding running, and there are a variety of impressions the driver receives from the vehicle during running. Therefore, an expected running characteristic is not necessarily obtained if the running environment changes or the vehicle is driven by another driver. As a result, so-called driveability may deteriorate.
Thus, one type of vehicle has been developed which is arranged to manually select running characteristics, such as a power output characteristic (or acceleration characteristic) and a suspension characteristic, concerning the behavior of the vehicle, by operating a mode selection switch. Namely, the vehicle is arranged to manually select a drive mode from, for example, a sporty mode in which the vehicle runs with an excellent accelerating ability, and the suspension is set to be somewhat hard, a normal mode in which the vehicle accelerates at a relatively low rate, and has a relatively soft suspension characteristic, and an eco mode in which the fuel economy or efficiency is prioritized, by operating the switch.
In addition, Japanese Patent Application Publication No. 10-77894 (JP-A-10-77894) describes a system that is configured to estimate the driving orientation of a vehicle on the basis of an output operation amount of the vehicle. The system described in JP-A-10-77894 is configured to determine a maximum value of a throttle valve opening degree that serves as the output operation amount of the vehicle and, when a deviation between the maximum value of the throttle valve opening degree and a throttle valve opening degree after a lapse of a predetermined period of time from when the throttle valve opening degree attains the maximum value is larger than a predetermined criterion value, prohibit estimation of the driving orientation based on the throttle valve opening degree. Specifically, for example, it is determined whether there is a so-called chip-in operation, such as steep depression and release operations of an accelerator pedal in a short period of time, that occurs depending on a driver's habit or a road condition, and, when it is determined that there is the chip-in operation, estimation of the driving orientation is prohibited.
In addition, Japanese Patent Application Publication No. 8-28640 (JP-A-8-28640) describes a control system for a vehicle equipped with a continuously variable transmission. The control system is configured to detect the gradient of a road (or the gradient resistance of the vehicle) and then filter the detected gradient using a low-pass filter to thereby prevent hunting of shift control due to a slight variation in the gradient.
The systems described in JP-A-06-249007 is configured to change a driver's driving orientation or a running characteristic on the basis of the longitudinal acceleration of the vehicle or a driver's accelerator operation. Therefore, by detecting or estimating the behavior of the acceleration of the vehicle, it is possible to estimate a driver's driving orientation and then incorporate the estimated driver's driving orientation into vehicle behavior control. However, for example, when the driver conducts such a driving operation as described in JP-A-10-77894, such as depression and release of an accelerator pedal and depression of a brake pedal, the variation component of the acceleration of the vehicle due to the influence of such a driving operation is incorporated as a so-called noise component and, as a result, the accuracy of estimating a driving orientation may possibly decrease. Different from the above, for example, when the vehicle runs on a big bumpy road surface, a road surface with a change in gradient, or the like, the variation component of the acceleration of the vehicle due to the influence of the running road surface is incorporated as a so-called noise component and, as a result, the accuracy of estimating a driving orientation may possibly decrease. In this way, in the existing art, there is still room for improvement in the accuracy of estimating a driver's driving orientation and adequate incorporation of a driver's request or driving orientation into a running characteristic.